Control circuit for dimming an electrochromic mirror glass of a rearview mirror of a motor vehicle

Abstract

A rearview mirror incorporates the use of electrochromic mirror glass capable of dimming via electronic controls. The electrochromic mirror glass dims when glare from vehicle driving aft of the motor vehicle impinge on the rearview mirror. The rearview mirror includes a control circuit with a single sensor. The sensor receives glare from aft and ambient light forward the motor vehicle. A light conductor guides light from the two directions. A sensor receives the light from the two directions and is able to discern between the glare light and the ambient light, by filtering the light received from each direction based on color. One color is received from one location and not from the other. The sensor is sensitive to wavelengths and can identify the magnitude of flux received in each color. This allows the interior rearview mirror to identify situations that are appropriate for dimming the electrochromic mirror glass.

1 .- 8 . (canceled) 
     
     
         9 . A method of dimming an electrochromic mirror glass comprising:
 filtering a first light to create a filtered first light;   transmitting the filtered first light to a sensor;   filtering a second light to create a filtered second light;   transmitting the filtered second light to the sensor;   measuring a first luminous flux of the filtered first light;   measuring a second luminous flux of the filtered second light;   comparing the first and second luminous fluxes to create a luminous flux difference; and   dimming the electrochromic mirror glass when the luminous flux difference exceeds a predetermined value.   
     
     
         10 . A method as set forth in  claim 9  wherein the step of filtering the first light includes the step of filtering the first light by a first wavelength. 
     
     
         11 . A method as set forth in  claim 10  wherein the step of filtering the second light includes the step of filtering the second light by a second wavelength differing from the first wavelength.